• Journal of Korea Water Resources Association
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• v.46 no.8
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• pp.821-831
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• 2013

Recently image velocimetries, including particle image velocimetry (PIV) and surface image velocimetry (SIV), are often used to measure flow velocities in laboratories and rivers. The most difficult point in using image velocimetries may be how to determine the sizes of the interrogation areas and the measurement uncertainties. Especially, it is a little hard for unskilled users to use these instruments, since any standardized measuring techniques or measurement uncertainties are not well evaluated. Sometimes the user's skill and understanding on the instruments may make a wide gap between velocity measurement results. The present study aims to evaluate image velocimetry's uncertainties due to the changes in the sizes of interrogation areas and searching areas with the error analyses. For the purpose, we generated 12 series of artificial images with known velocity fields and various numbers and sizes of particles. The analysis results showed that the accuracy of velocity measurements of the image velocimetry was significantly affected by the change of the size of interrogation area. Generally speaking, the error was reduced as the size of interrogation areas became small. For the same sizes of interrogation areas, the larger particle sizes and the larger number of particles resulted smaller errors. Especially, the errors of the image velocimetries were more affected by the number of particles rather than the sizes of them. As the sizes of interrogation areas were increased, the differences between the maximum and the minimum errors seemed to be reduced. For the size of the interrogation area whose average errors were less than 5%, the differences between the maximum and the minimum errors seemed a little large. For the case, in other words, the uncertainty of the velocity measurements of the image velocimetry was large. In the viewpoint of the particle density, the size of the interrogation area was small for large particle density cases. For the cases of large number of particle and small particle density, however, the minimum size of interrogation area became smaller.

• Journal of Conservation Science
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• v.37 no.5
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• pp.545-556
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• 2021

In this study, we aimed to elucidate the materialistic characteristics of 11 pieces of earthenware belonging to the Neolithic and Bronze Age excavated from Jeongseon Auraji, South Korea. As a result, the chemical composition of earthenwares belonging to the early Bronze Age was distributed in the intermediate area between the Neolithic and Bronze Age earthenwares, but no significant difference was confirmed based on their manufacturing period. Upon comparison, the earthenwares excavated from Jeongseon Auraji site were found to comprise less acidic components than those excavated from Yeongdong, and are characterized by the alkaline components depending on the excavated site. In the rare earth elements distribution pattern, all the analyzed earthenwares exhibited similar pattern, confirming that the raw materials present in the clay were the same. As a result of microstructure analysis, the clay particles and voids were found to be irregularly distributed in the analyzed earthenwares. Neolithic earthenwares exhibited many irregular voids, and an arrangement of aluminosilicate, including feldspar, was observed along with the clay substrate. Furthermore, we confirmed that the empty space in early Bronze Age earthenwares was filled with fine particles and cube crystals. Moreover, the main mineral phase of earthenwares excavated from Jeongseon Auraji exhibited similar composition, and therefore, there was no significant difference in the firing temperature of these earthenwares. The firing temperature of the earthenwares ranged from 750 to 850℃.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.796-802
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• 2018

The effects of inner liquid sloshing on vessel motions are a well-known factor. It was investigated experimentally and numerically. In this regard, the study of many efforts to reduce natural phenomena of vessel motions by adopting special devices especially for roll motions. Among many devices, inserting baffles in the inner liquid tank is very common. In this study, one investigated the vessel motions with inner sloshing tanks with baffles inside. For the numerical simulation, one employed a dynamically coupled program between boundary-element-method-based vessel motion analysis program and a particle-based computational fluid dynamics program. Comparing corresponding experimental results validated the dynamically coupled program. The validated coupled program was used to simulate vessel motions, including sloshing effects with various lengths of inner baffles. The simulation results show that not only the filling ratio of inner liquid, but also the length of clearance due to baffles influenced the vessel motions. The significant point of this study was that the natural frequency of vessel motions can be maintained irrespective of the amount of filling ratio through adjustment of the clearance. In a future study, the effects of various numbers of baffles with various clearances would be conducted to percuss the possibility of vessel motion control with inner liquid sloshing effects.

• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.49-58
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• 2010

This paper presents experimental results of a series of 1-g shaking table model tests performed on end-bearing single piles and pile groups to investigate the effect of particle size on the dynamic behavior of soil-pile systems. Two soil-pile models were tested twice: first using Jumoonjin sand, and second using Australian Fine sand. In the case of single-pile models, the lateral displacement was almost within 1% of pile diameter which corresponds to the elastic range of the pile. The back-calculated p-y curves show that the subgrade reaction of the Jumoonjin-sand-model ground was larger than that of the Australian Fine-sand-model ground at the same displacement. This phenomenon means that the stress-strain behavior of Jumoonjin sand was initially stiffer than that of Australian Fine sand. This difference was also confirmed by resonant column tests and compression triaxial tests. And the single pile p-y backbone curves of the Australian fine sand were constructed and compared with those of the Jumoonjin sand. As a result, the stiffness of the p-y backbone curves of Jumunjin sand was larger than those of Australian fine sand. Therefore, using the same p-y curves regardless of particle size can lead to inaccurate results when evaluating dynamic behavior of soil-pile system. In the case of the group-pile models, the lateral displacement was much larger than the elastic range of pile movement at the same test conditions in the single-pile models. The back-calculated p-y curves in the case of group pile models were very similar in both sands because the stiffness difference between the Jumoonjin-sand-model ground and the Australian Fine-sand-model ground was not significantly large at a large strain level, where both sands showed non-linear behavior. According to a series of single pile and group pile test results, the evaluation group pile effect using the p-multiplier can lead to inaccurate results on dynamic behavior of soil-pile system.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.295-295
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• 2014

일반적으로 박막 태양전지의 효율은 박막 종류에 따른 광 흡수율에 의해 결정되며, 이는 증착한 박막의 두께에 의해 결정된다. 증착한 박막의 두께가 두꺼워질수록 광 흡수율은 증가하지만, 박막 두께가 지나치게 두꺼워지면 열화 현상으로 인한 모듈의 효율 감소가 생기므로 적절한 박막의 두께가 요구된다. 특히 a-Si:H의 경우 가시광 영역에서 높은 흡수계수를 가지고 있어서 얇은 박막 두께로도 태양전지의 제작이 가능하지만, 동일한 박막 두께에서 효율을 더욱 향상시키기 위한 다양한 광 포획 기술에 대한 연구가 많이 진행 되고 있다. 본 연구에서는 자외선을 이용한 nano-imprint lithography 기술을 이용하여 a-Si:H 태양전지의 유리기판 위에 pattern을 삽입하여 광 산란 효과를 향상 시키고자 하였다. 또한 유리기판의 굴절률 (n=1.5)과 투명전극의 굴절률 (n=1.9)의 중간 값을 갖는 ZnO nanoparticles (n=1.7)이 분산 된 imprinting resin을 사용함으로써 점진적으로 굴절률을 변화시켜, 최종적으로 a-Si:H 층까지의 광 투과율을 높이고자 하였다. 제작한 기판의 종류는 다음과 같다. 첫 번째 기판으로는 유리기판 위에 ZnO nanoparticles이 분산 된 imprinting resin을 spin-coating 하여 점진적인 굴절률의 변화에 의한 투과도 향상을 확인하고자 하였다. 두 번째 기판으로는 규칙적인 배열을 갖는 micro 크기의 패턴을 형성하였다. 마지막으로는 불규칙한 배열을 갖는 nano 크기와 micro 크기가 혼재 된 패턴을 형성하여 투과도 향상과 동시에 빛의 산란을 증가시키고자 하였다. 후에 이 세가지 종류를 기판으로 사용하여 a-Si:H 기반의 박막 태양전지를 제작하였다. 먼저 제작한 박막 태양전지용 기판의 광학적 전기적 특성을 분석하였다. 유리 기판 위에 형성한 패턴에 의한 roughness 변화를 확인하기 위해 atomic force microscopy (AFM)를 이용하여 시편의 표면을 측정하였다. 또한 제작한 유리 기판 위에 투명 전극층을 형성 후, 이로 인한 전기적 특성의 변화를 확인하기 위해 hall measurement system을 이용하여 sheet resistance, carrier mobility, carrier concentration 등의 특성을 측정하였다. 또한, UV-visible photospectrometer 장비를 이용하여 각 공정마다 시편의 광학적 특성(투과도, 반사도, 산란도, 흡수도 등)을 측정하였고, 최종적으로 제작한 박막 태양전지의 I-V 특성과 외부양자효율을 측정하여 태양전지의 효율 변화를 확인하였다. 그 결과 일반적인 유리에 기판에 제작된 a-Si:H 기반의 박막 태양전지에 비해, ZnO nanoparticles이 분산 된 imprinting resin을 spin-coating 하여 점진적인 굴절률 변화를 준 것만으로도 약 12%의 태양전지 효율이 증가하였다. 또한, micro 크기의 패턴과 nano-micro 크기가 혼재된 패턴을 형성한 경우 일반적인 유리를 사용한 경우에 비해 각각 27%, 36%까지 효율이 증가함을 확인하였다.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.50-56
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• 2016

Spherical lithium manganese oxide spinel, $Li_{1.10}Mn_{1.86}Al_{0.02}Mg_{0.02}O_4$ was prepared by wet-milling, spray-drying, and sintering process. In the spray-drying process, solid content in slurry was varied from 20 to 30 wt%. In the sintering process, the precursors have been sintered under air or $O_2$ atmosphere. While the as-prepared samples exhibit excellent electrochemical properties at room temperature, the discharge voltage profiles at 5.0C are very different one from another. The origin for the difference especially at initial state of discharge is oxygen defect. The sample prepared in air has larger capacity related to the plateau at 3.3 V (vs. $Li/Li^+$) which is caused by the oxygen defects than the one prepared in $O_2$. The difference of discharge voltage profiles especially at the final state of discharge comes from different diffusion rate of $Li^+$ ions. The sample prepared from 30 wt% solid content of slurry shows twice higher diffusion rate than the samples prepared from 20 wt% solid content, which is attributed to better compactness between primary particles for the sample prepared from 30wt % solid content than the one prepared by 20 wt%.

• Analytical Science and Technology
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• v.26 no.4
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• pp.245-255
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• 2013

Identification of paint on victim's clothing and a vehicle are valuable for forensic examination when investigating hit-and-run accidents. Automotive paints on clothes are used to prove a victim caused by traffic accident and to identify a suspected vehicle. The comparison of transferred paints between victim's vehicle and suspected vehicle can be an important evidence in reconstructing the accident situation and in discovering the truth. The paints such as white, yellow, red, blue, or black are hard to examine particle shape under a stereomicroscope because of it is not included aluminum, pearl, and mica flakes in the pigments. The aim of this study under forensic aspect is to compare pigment among basecoat layers of solid paints by identifying inorganic elemental compositions and binder resins of pigments using by micro-FT-IR and micro-XRF spectrometer. The pigment samples were analyzed by using two methods of FT-IR: Reflectance and ATR method. Two methods of FT-IR were useful in discriminating binder resins of pigments by comparing characteristic peaks and patterns of spectra. Also, XRF spectrometer could identify the elemental compositions in inorganic pigments of trace paints which are difficult to compare the identification by FT-IR.

• Food Engineering Progress
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• v.21 no.3
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• pp.273-279
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• 2017

Curcumin have various health-beneficial properties in numerous studies. However, its bioavailability is low due to its limited intestinal uptake and rapid metabolism. This study aimed to evaluate the pharmacokinetics of newly developed sub-micron particle curcumin with increased water dispersibility (Theracurmin(R) CR-033P). Plasma curcumin levels were measured at 0, 1, 2, 4, 8 h after Theracurmin(R) CR-033P intake using high-performance liquid chromatography. For analyzing pharmacokinetics of Theracurmin(R) CR-033P, eighteen healthy subjects were recruited and received Theracurmin(R) CR-033P at a single oral dose containing curcumin 30 mg. $C_{max}$ was 28.14 ng/ml, and the area under the curve for 8 h was estimated to be 104.36 ng/ml. Based on the area under the plasma concentration (AUC), the bioavailability of sub-micron particle curcumin was higher 22-, 35-, 28-fold than native curcumin in men, women, and all subjects, respectively. For comparing by formulation, seven healthy subjects were recruited and received two type of treatment: (1) existing dosage form 300 mg (contained curcumin 30 mg) ${\times}$ 3 capsule, (2) high dosage form 300 mg (contained curcumin 90 mg) ${\times}$ 1 capsule + placebo 300 mg ${\times}$ 2 capsule. In the cross-over study, there was no significant differences in $C_{max}$ and AUC of plasma curcumin. In conclusion, submicron particle curcumin with increased water dispersibility significantly improved its oral bioavailability and women absorbed curcumin more effectively than men. Different formulation of Theracurmin(R) CR-033P has shown equivalent to the reference in terms of pharmacokinetics.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.5-14
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• 2013

Coarse granular geomaterials containing large gravels are broadly used for construction of large geotechnical systems such as dams, levees, railways and backfills. It is necessary to evaluate deformation characteristics of these materials for dynamic analysis, e.g. seismic design. This study presents evaluation of dynamic deformation characteristics of coarse materials using large scale resonant column testing apparatus, which uses specimens with 200 mm in diameter and 400 mm in height, and the effects of gradation characteristics on maximum shear modulus, shear modulus reduction curve and damping characteristics were investigated. From experimental study using rock-fill materials for a dam, we could see that the largest or mean particle size affects the shape of shear modulus reduction curve. When the specimens are prepared under the same conditions for maximum particle size, the coefficient of uniformity affects the confining stress exponent of maximum shear modulus. It could be concluded that the maximum particle size is an factor which affects shear modulus reduction curve, and that the coefficient of uniformity is for small strain shear modulus, especially for the sensitivity to confining stress.

• Journal of Conservation Science
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• v.32 no.3
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• pp.417-423
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• 2016

The effect of the glue solution were investigated in the grinding and elutriation process for manufacturing of White clay pigment. In grinding process, glue solution decreased the production of a too fine powder and enhanced the degree of sorting of ground pigments. The grinding performance and limit are generally influenced by the frictional force. Therefore, the friction force was measured in accordance with the grinding conditions. As a result of measuring a friction force, when using glue solution it showed the lowest friction. Finally, the application of glue solution in grinding process is believed to enhance the degree of sorting of ground pigments by reducing frictional force. In elutriation process, the application of glue solution enabled the screening of larger particles in the same conditions by reducing the sedimentation velocity. This result is due to increase in the viscosity of the glue solution according to glue concentration. As a result, the application of glue solution in elutriation process is though to enlarges the range of the selectable particle size and to enable the segmentation of the particles.